Question

What is a resonance structure? Is it possible to isolate one resonance structure of a compound for analysis? Explain.

Short answer

A resonance structure is one of multiple representations of a molecule. They cannot be isolated, as only the resonance hybrid exists.

Step-by-step solution

Define Resonance Structure

A resonance structure is one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure. These structures illustrate the delocalization of electrons within the molecule.

Explain the Concept of Resonance

In molecules where resonance occurs, the actual structure is a hybrid of all possible resonance structures. This hybrid cannot be exactly described by any single structure, but rather shows a distribution of electron density that is a blend of all structures.

Discuss Isolation of Resonance Structures

It is not possible to isolate a single resonance structure since they are not distinct entities. Each resonance form contributes to the overall, observed structure described by a resonance hybrid, which is the only form that truly exists in nature.

Key concepts

Lewis structures

Lewis structures are diagrams that depict the bonding between atoms within a molecule, as well as any lone pairs of electrons that may exist.
These structures use lines to represent chemical bonds and dots to signify lone electron pairs.
They are crucial for understanding molecular geometry and how atoms are connected. With Lewis structures, you can visualize:

• Bonding electrons: Shared pairs of electrons forming a covalent bond.
• Lone pairs: Electrons that are not shared but belong to a single atom.

Lewis structures provide a straightforward way to predict molecular properties, such as arrangement and shape. However, for some molecules, a single Lewis structure is not enough to depict the electron distribution accurately, which leads us to consider resonance structures.

electron delocalization

Electron delocalization refers to the concept where electrons are not confined to a single bond or location within a molecule.
Instead, they are spread out or shared across several atoms. This phenomenon is particularly significant in structures that exhibit resonance. In a molecule with resonance:

• Electrons can move through the pi bonds, providing extra stability.
• The electron density is distributed over more atoms, rather than being localized.

This delocalization results in enhanced stability due to the spread of electronic charge. Alternatively, electron delocalization in resonance structures is why not a single Lewis structure can adequately represent the true picture of electron distribution.

resonance hybrid

A resonance hybrid is the actual structure of a molecule that displays resonance, embodying characteristics of all possible resonance structures.
This concept explains why it is impossible to isolate any one resonance structure for analysis. In a resonance hybrid:

• The actual electron distribution is a weighted average of all the resonance forms.
• The hybrid is generally more stable than any individual resonance structure, due to electron delocalization.

Resonance hybrids provide a more accurate depiction of molecular structure, demonstrating that the real molecule exists as a blend, rather than fluctuating between forms. This hybrid model reflects consistent stability and electron distribution that individual resonance structures cannot independently display.